WellPoint Inc. said its second-quarter profit slipped as the health insurer recorded higher expenses, masking revenue and enrollment growth.

The decline in earning was smaller than expected, however, and the company again raised its outlook for the year. It now expects its per-share profit to top $8.60, compared with its prior forecast for more than $8.40 a share. WellPoint reiterated its expectation for operating revenue above $73.5...